Have Mirena Coil. Abdominal Pain, Lower Back Pain. Negative Pregnancy Test. Tiredness, Brown Discharge. Opinion?

Hi my name is Natasha and I have the Mirena coil in just over a year since my daughter was born. I've been experiencing very bad pain in my abdomen and in my lower back and every pregnancy test is negative. I'm constantly tired all the time and i'm getting deadness along my shins when I walk. I've been really hormonal and keep lashing out at every little thing. I've been getting this sticky brown coloured discharge the last couple of weeks also and it smells a bit off. I've been put onto numerous antibiotics to kill this discharge and it doesn't seem to be going away. My doctor doesn't seem to no the source of the problem could you please give me your opinion on this matter because it's starting to bother me at this stage. Thank you.